"Server shut down due to unhandled script surveillance exception" (??

It doesn't let me interact in my worlds, it takes me out I've never had such a problem, That error always marks me (image)  it started from the update Can you fix it?

I enter my world with mods as I have always done but now it takes me out I had never happened. 

I wanted to play with my niece but it's impossible to HELP!